A small glass once in a while to curb cravings won't harm, but don't make it a habit. It can cause bad acidity and gas, which is already a headache during pregnancy.
Honestly, when you are busy, grabbing a cold drink seems easy, but Thums Up is just empty sugar. Keep a bottle of buttermilk or coconut water handy at work instead.
I felt so much craving for cold fizzy drinks in my second trimester! I had a few sips of Thums Up occasionally, but felt guilty later, so I switched to home-made fresh lime soda.
In our home, elders strictly advise against aerated drinks like Thums Up due to high sugar and caffeine. It is better to avoid it, but you can always ask your doctor if a small sip is okay.
Honestly, Thums Up has high sugar, caffeine, and artificial carbonation, which isn't great for the baby. Having it once in a blue moon is fine, but check with your doctor first.